Dental system for treatment of periodontal pockets laser light

ABSTRACT

A dental system for treatment of periodontal pockets using laser light, comprising a handpiece for directing laser light and a coolant spray towards a target tissue area to be treated, including an optical fiber duct, a water duct and an air duct, and an apparatus including a laser and a controller for water and air flow.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/DK99/00057 which has an Internationalfiling date of Feb. 8, 1999, which designated the United States ofAmerica.

FIELD OF THE INVENTION

The present invention relates to a dental system for treatment ofperiodontal pockets using laser light and having a handpiece with anoptical fibre for directing laser light towards a target tissue area tobe treated.

BACKGROUND OF THE INVENTION

It is known to utilise laser light for treatment of periodontal pockets.

During treatment laser light heats plaque by illumination therebydestroying living cells in the plaque so that a subgingival infection isstopped by laser treatment.

Lasers that operate at a wavelength that is moderately absorbed in waterare used for this treatment. When the laser power density (W/mm2) atilluminated cells is sufficient, cellular water is heated by energyabsorption causing a temperature rise in the cell that destroy heatedcells.

During treatment, it is essential not to heat or damage surroundingtissue. Residual heat may affect the nerve of the tooth causing pain tothe patient and/or may cause tissue to char and become necrotic. Thus,it is desirable to minimise transmission of conducted heat to underlyingand surrounding tissue.

It is therefore desired to accurately control the amount of light energytransferred to plaque, calculus, tissue to be incised, etc, to betreated. The amount of energy must be sufficient for effectivelytreating matter, such as plaque, calculus, tissue, and, simultaneously,the amount of residual energy heating surrounding tissue must be too lowto heat the tissue.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a denial system fortreatment of periodontal pockets using laser light for laser surgery,such as laser gingivectomy, periodontal pocket curettage, etc, withoutheating surrounding tissue.

According to a first aspect of the invention, the above-mentioned andother objects are fulfilled by a dental system for treatment ofperiodontal pockets using laser light, comprising a handpiece fordirecting laser light and a coolant spray towards a target area to betreated. The handpiece comprises a housing with an input end and anoutput end and holds an optical fibre duct for receiving and holding anoptical fibre and extending within the housing from the input end to theoutput end. During operation of the system, an optical fibre with afibre output end for emission of the laser light is positioned in theoptical fibre duct. Further, the optical fibre duct may hold a seal thatis adapted to receive and hold the optical fibre in water tightengagement with the optical fibre duct. The housing also has an air ductfor transmission of compressed air and extending within the housing fromthe input end to the output end and a water duct for transmission ofwater and extending within the housing from the input end The water ductleads into the optical fibre duct within the housing between the outputend and the seal so that water flowing through the water duct leaves thehousing at the output end through the optical fibre duct. The treatinglaser light to be emitted from the fibre output end is supplied by alaser in an apparatus that is connected to the fibre so that light fromthe laser is coupled into the fibre.

When treating laser light is emitted from the fibre output end, a spraycoolant of mixed air and water is simultaneously emitted from the outputend of the handpiece housing providing cooling of tissue surrounding thetreated area illuminated by the laser light. Thus, the apparatus furthercomprises a water control member that is adapted to be interconnectedbetween a water supply and the water duct and to control the amount ofwater flowing into the water duct, and an air control member that isadapted to be interconnected between a supply of compressed air and theair duct and to control the amount of compressed air flowing into theair duct.

The apparatus also has a controller for controlling the operation of thesystem and being connected to the water control member and the aircontrol member and being adapted to set the amount of water flowing intothe water duct in the range from 5 ml/min to 50 ml/min, preferably from10 ml/min to 30 ml/min, and more preferred to approximately 20 ml/min.

Further the controller is adapted to set the pressure of compressed airflowing into the air duct so that a coolant spray of mixed air and wateris formed. This may be done by provision of a user interface that isconnected to the controller and that is utilised by an operator of thesystem to enter parameter values of the system to be set by thecontroller. The operator may in this way increase the pressure ofcompressed air until formation of the spray of mixed air and water isvisually detected.

The amount of water forming the water spray is selected so that theamount is sufficient to effectively cool surrounding tissue not to betreated by the laser light while being less than an amount that wouldabsorb so much laser light that treatment would be inhibited.

According to an important aspect of the present invention, thewavelength and the power level of the laser light are selected so thatonly matter that abuts the fibre output end is heated when illuminatedby the laser light. Thus, there is no risk of harming tissue that isaccidentally illuminated by laser light emitted from the fibre outputend as the energy density in the emitted laser light decreases rapidlywith distance from the fibre output end.

According to another important aspect of the present invention,efficient cooling of tissue surrounding target area being treated by thelaser light is provided by directing a coolant spray of air and watertowards the surroundings of the fibre output end. As the water leavesthe housing through the fibre duct and at least some of the watercontinues to flow along the surface of the fibre, accurate directing ofthe air and water spray along a longitudinal axis of the fibre isprovided. The amount and composition of the air and water spray and theamount of light energy supplied to the treatment area are selected sothat efficient cooling of the surroundings of the treatment area isprovided thereby effectively preventing conduction of heat from thetreatment area while simultaneously raising the temperature of matterabutting the fibre output end sufficiently to destroy and preferablyremove the matter.

Light of 1 μm wavelengths are moderately absorbed in water and theextinction length in soft tissue is about 1 to 3 mm. However, colour andstructure of tissue have a great influence on absorption of light inthis wavelength range and pigmented tissue absorbs light in thiswavelength range efficiently. The light is for example absorbed in bloodcausing photocoagulation of blood and this effect is advantageouslyutilised during treatments with the present system.

Typically, the treatment is initiated when the fibre output endaccumulates dark particles that is heated through light absorption.Plasma, a super-heated gas, may form on the surface abutting the fibreoutput end. Plasma absorbs the light and conducts heat to the matter tobe treated, such as gingival tissue, plaque, calculus, etc. Plaque andtissue to be treated typically evaporates and calculus becomes brittleduring treatment.

It should be recognised that many parameters of the treating lightdetermine the effect of the treatment. Such parameters comprise thelaser wavelength, laser power, laser waveform, tissue opticalproperties, tissue thermal properties, way of cooling, etc. The numberof possible combinations of these parameters is infinite, many of whichwould result in inefficient treatment and/or unacceptable damage totissue that should not be treated. Thus, the present invention is basedon intensive research and clinical tests in the field of treatment ofperiodontal pockets using laser light.

As will be described in more detail below, this intensive research hasrevealed that it is possible to effectively treat periodontal pocketswithout damaging healthy tissue with a system according to the presentinvention.

The combination of average power in the emitted light and the repetitionrate of emitted light pulses has to be set in a power range and afrequency range, respectively, wherein the above-mentioned thermaleffects occur without a risk of damaging healthy tissue. It has beenfound that treatment with repetition frequencies below 50 Hz hasresulted in unsatisfactory clinical results and that repetitionfrequencies below 70 Hz can be safely utilised without heatingsurrounding tissue at average power levels ranging from 1 to 10 W.Preferably the average power ranges from 3 W to 8 W. For pocketcurettage it is preferred to set the average power ranging from 4 W to 6W, and most preferred the average power is approximately 5 W and forlaser surgery it is preferred to set the average power ranging from 5 Wto 8 W, and more preferred from 6 W to 7 W.

The repetition frequency preferably ranges from 50 Hz to 70 Hz, morepreferred from 55 Hz to 65 Hz, and still more preferred the repetitionfrequency is approximately 60 Hz.

Simultaneously, the duration of the light pulses must be within therange wherein sufficient energy is delivered to effectively heat matterto be treated without the average power attaining unsafe levels.According to the present invention it is preferred that the duration ofthe light pulses ranges from 150 μs to 500 μs, preferably from 200 μs to300 μs, more preferred that the duration is approximately 250 μs.

It is an important advantage of the present invention that the emittedlaser light causes photocoagulation of blood so that possible bleedingof treated tissue is quickly stopped.

The laser may be any laser capable of emitting light of suitablewavelength and with sufficient power for illuminated matter to betreated, such as Nd YAG lasers, NCG lasers, diode lasers, etc.

A Nd YAG laser emits light at a wavelength of 1.064 μm. The Nd YAG laseris particularly well suited as a light source in a dental system fortreatment of periodontal pockets as water has a moderate energyabsorbance at 1.064 μm so that heating of matter abutting the fibreoutput end is provided while simultaneously allowing water in thecoolant spray impeding on surrounding matter to effectively cool thesurroundings of the matter being treated. Further, the Nd YAG laser iscapable of reliably delivering the required laser power.

The optical fibre of the handpiece according to the present inventionmay be any fibre, such as an optical fibre made of pure silica, etc,that is suitable for transmission of light emitted from the laser andthat is made of a material that allows repeated bending of the fibre sothat an operator can freely manipulate the handpiece, e.g., in order toinsert the fibre output end into a periodontal pocket of a patient. Itis preferred that the outer diameter of the fibre ranges from 300 μm to600 μm, and presently it is preferred to use fibres with an outerdiameter of approximately 400 μm or approximately 600 μm.

For an operator of the system to be able to treat a suitable area duringa suitable time period, it is presently preferred that the laser isadapted to emit light for a period ranging from 10 s to 1 minutes uponuser activation, and more preferred for a period ranging from 20 s to 50s upon user activation, and even more preferred for a period ofapproximately 30 s upon user activation.

The user interface may comprise a foot pedal for activation of thesystem so that light is emitted from the fibre output end uponactivation of the foot pedal.

The controller may comprise at least one timer for accumulation of thetime during which light has been emitted by the system. A timer valuemay be displayed to the operator of the system on the user interface.The timer value may be utilised by the operator of the system forcalculation of cost of a treatment.

A timer value may be read by a service technician during maintenance ofthe system, e.g., in order to decide whether preventive service taskshave to be performed or not.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, a preferred embodiment of a dental system fortreatment of periodontal pockets using laser light will be describedwith reference to the drawings, wherein

FIG. 1 is a front view of a system according to the invention,

FIG. 2 is a rear view of a system shown in FIG. 1,

FIG. 3 is a front schematic of the system shown in FIG. 1 without coverplates,

FIG. 4 is a side schematic of the system shown in FIG. 1 without coverplates,

FIG. 5 is another side schematic of the system shown in FIG. 1 withoutcover plates,

FIG. 6 shows schematically the construction of a handpiece according tothe invention,

FIG. 7 shows the supply ducts in the handpiece shown in FIG. 6,

FIG. 8 shows a front panel of the user interface of the system shown inFIG. 1

FIG. 9 is a flow diagram of the operation of the system shown in FIG. 1,

FIG. 10 is a circuit diagram of the control signals of the system shownin FIG. 1,

FIG. 11 is a circuit diagram of the high voltage supply interconnectionsof the system shown in FIG. 1,

FIG. 12 is a circuit diagram of the AC line interconnections of thesystem shown in FIG. 1,

FIG. 13 is a circuit diagram of the 24 V_(DC) interconnections of thesystem shown in FIG. 1,

FIG. 14 shows schematically a cooling system of the system shown in FIG.1,

FIG. 15 shows schematically an air and water spray supply system of thesystem shown in FIG. 1,

FIG. 16 is a circuit diagram of the laser output power control system ofthe system shown in FIG. 1,

FIG. 17 is a circuit diagram of a shutter system of the system shown inFIG. 1.

FIG. 18 shows a fibre cutter,

FIG. 19 shows insertion of an optic fibre into the cutter shown in FIG.18,

FIG. 20 shows stripping off a protective layer around an optic fibreinserted into the cutter as shown in FIG. 19,

FIG. 21 shows a stripped fibre with a desired length of optic fibreexposed,

FIG. 22 illustrates cut off of a used piece of fibre with a diamond pen,

FIG. 23 illustrates positioning of a fibre tip in contact with gingivaat the entrance of a pocket,

FIG. 24 illustrates the fibre tip having reached the bottom of thepocket,

FIG. 25 illustrates withdrawal of the fibre from the pocket,

FIG. 26 illustrates a bevelled incision at the bottom of the pocketthrough the gingiva and abutting the tooth surface,

FIG. 27 illustrates the site shown in FIG. 26 after removal of excisedtissue,

FIG. 28 illustrates bevelled incisions on the buccal and oral aspects atinterproximal sites,

FIG. 29 illustrates separation with a fibre of dissected free tissuehaving been lifted with a curette or forceps,

FIG. 30 illustrates treatment of exposed root surfaces with laser lightfor vaporising bacteria,

FIG. 31 illustrates a reverse bevel incision used for treatment ofinfrabony defects,

FIG. 32 illustrates removal with a curette of pocket epithelium aftergradual deepening of the incision shown in FIG. 31,

FIG. 33 illustrates horizontal incisions directed towards the base ofthe pocket at the buccal and lingual sides of a tooth,

FIG. 34 illustrates vertical intracrevicular incisions produced at bothsides of the tooth,

FIG. 35 illustrates horizontal incision for excision of granulationtissue in the furcation, and

FIGS. 36-38 illustrate epithelization of a wound after laser surgery.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIGS. 1-5, the system 10 according to the present inventioncomprises a handpiece 12 with an fibre output end 14 for treatment ofe.g. periodontal pockets. Light to be emitted from the fibre output end14 is supplied by a laser 16 that is coupled to the fibre with a fibrecoupler 18. The laser 16 is pumped by a flash lamp that is ionised by avoltage pulse generated by a simmer module 22. When the flash lamp 20gas is ionised the simmer module 22 maintains a small simmer current.The simmer module 22 provides about 1000 V_(DC) to the flash lamp 20.The simmer module 22 then generates 1 ms pulses of 200-300 V_(DC) at 27Hz to a trigger transformer until the flash lamp 20 gas ionises. Avoltage sensor circuitry inside the simmer module 22 detects the gasionisation and stops the simmer pulses. After the initiation the voltagedrops to approximately 135 V_(DC).

A high voltage power supply 34 generates a 400 V_(DC) output supplied tothe capacitors 24, 26.

As also shown in FIG. 15, water and air for the mixed air and waterspray generated at the fibre output end 14 at the handpiece 12 issupplied from a water inlet 36. From the water inlet 36 water flowsthrough a reduction valve 38 and thereafter through a linearlycontrolled solenoid valve 40 that controls the amount of water deliveredto the handpiece 12. The valve 40 is controlled by the controller 32.Likewise, air flows from an air inlet 42 through a reduction valve 44and thereafter through a linearly controlled solenoid valve 46 thatcontrols the amount of air delivered to the handpiece 12. The valve 46is also controlled by the controller 32.

High voltage for driving the flash lamp 20 is supplied from twocapacitors 24, 26. The high voltage is controlled by an IGBT 28 whichagain is controlled by an IGBT drive circuit 30. A trigger signal forthe IGBT drive circuit 30 is supplied by a controller 32.

FIGS. 6 and 7 shows schematically the construction of a handpieceaccording to the invention for directing laser light and a coolant spraytowards a target area to be treated. The handpiece 12 comprises ahousing 48 with an input end 50 and an output end 52 and holds anoptical fibre duct 54 for receiving and holding an optical fibre 56 andextending within the housing 48 from the input end 50 to the output end52. During operation of the system, an optical fibre 56 with a fibreoutput end 14 for emission of the laser light is positioned in theoptical fibre duct 54. Further, the optical fibre duct 54 holds a seal58 that is adapted to receive and hold the optical fibre 56 in watertight engagement with the optical fibre duct 54. The housing 48 also hasan air duct 60 for transmission of compressed air and extending withinthe housing 48 from the input end 50 to the output end 52 and a waterduct 62 for transmission of water and extending within the housing 48from the input end 50. The water duct 62 leads into the optical fibreduct 54 within the housing 48 between the output end 52 and the seal 58so that water flowing through the water duct 62 leaves the housing 48 atthe output end 52 through the optical fibre duct 54.

FIG. 1 and FIG. 8 show a front panel 64 of the user interface of thesystem shown in FIG. 1.

EXAMPLES

When the system is used for dental treatments, the “periodontology”button (FIG. 9) is activated and the laser parameter are adjusted asdescribed below. The timer may be used for controlling total time oftreatment.

Further the length of the optical fibre is adjusted to correspond to thedepth of the pocket by means of a fibre cutter as shown in FIGS. 18a and18 b. The sliding device shown in FIG. 19 is adjusted to the desiredlength and the fibre covered with a protective layer is inserted intothe cutter. The protective layer is stripped off as shown in FIG. 20 bypressing the edges of the cutter while retracting the fibre from thecutter. This results in the exposure of the desired length of theoptical fibre as shown in FIG. 21. After end of treatment, the handpieceis disconnected from the system and sterilised in an autoclave. Beforestart of a new treatment, the autoclaved handpiece is connected to thesystem and a piece of optical fibre is cut off with a diamond pen asshown in FIG. 22. These measures prevent contamination of the handpieceand the fibre and transfer of e.g. bacteria from one patient to another.

Example 1 Pocket Curettage with Laser

Applications.

Treatment of periodontal pockets with PPD of 4-6 mm or deep pocketsduring the initial hygienic phase.

Laser Parameters

Power: 5 W Water: 4-7 Air: 3-5 Time: 30-120 seconds per site

Local anesthesia is not required.

Technique.

Adjust the length of the optic fibre according to the depth of thepocket scheduled for the treatment. During pocket curettage the laserfibre is always hold parallel to the root of the tooth. Activate thelaser, and place the fibre tip in contact with gingiva at the entranceof the pocket (FIG. 23). Then, slowly insert the fibre into the pocketby moving it in the buccolingual direction at proximal sites, while inthe mesio-distal direction at buccal or lingual sites. Placement of thefibre into the pocket is usually painless. The fibre, held in contactwith the soft tissues, is then slowly moved apically until the bottom ofthe pocket is reached. This procedure results in gradual vaporizing ofthe pocket epithelium, subgingival plaque and some granulation tissues(FIG. 24). The laser fibre, held in contact with the root surface, isthen moved coronally and withdrawn from the pocket in order to vaporizemicrobial debris on the root surface (FIG. 25). Remaining mineralizeddeposits, if present, are easily detected with a non-activated fibre andremoved with a curette. Usually, this procedure requires 30-120 secondsper site.

Example 2 Laser Surgery

Applications

Elimination of periodontal pockets with PPD>6 mm, gingival enlargement,furcation involvements. Prior to surgery, all patients have to completethe hygienic phase, which includes OH-instruction, removal of supra- andsubgingival deposits.

Laser Parameters

All laser surgeries should be performed using the following parameters:

Power: 6-7 W Water: 4-7 Air: 3-5

Local anesthesia usually is not required.

Technique

Supra-alveolar periodontal pockets or gingival hyperplasias

For treatment of these lesions laser gingivectomy is performed. Identifythe depth and type of pocket around each tooth scheduled for thetreatment. A beveled incision is made at the level of the bottom of thepocket through the gingiva onto contact with the tooth surface (FIG.26). The excised tissue is removed with a curette or forceps (FIG. 27).

At interproximal sites, the beveled incisions are made on the buccal andoral aspects (FIG. 28). Then, the dissected free tissue is lifted with acurette or forceps and separated from the interdental periodontium withthe laser (FIG. 29). The exposed root surfaces are then treated with thelaser for vaporizing bacteria (FIG. 30) and scaled, if calculus ispresent.

Infrabony Defects

In such defects, the bottom of the pocket is located below the bonelevel. Therefore, a “reverse bevel incision” is used for the treatmentof such lesions. The fibre is angled at approximately 45 degrees to thelong axis of the tooth (FIG. 31). The laser is activated and an initialincision is made. By gradually deepening the incision towards the bottomof the pocket, the pocket epithelium and the granulation tissue aredissected free and removed with a curette (FIG. 32). In case ofpost-surgical bleeding, move the fibre over the operated area for a fewseconds to coagulate the blood vessels. The exposed root surfaces arethen treated with the laser for vaporizing bacteria and scaled, ifcalculus is present.

Furcation-involved Teeth

For the treatment of degree II furcations, a gingivectomy is performedat the furcation area. Access to the furcation defect is obtained bymeans of horizontal incision with the laser fibre held horizontally anddirected to the base of the pocket onto contact with the tooth surface.The dissected soft tissue flap is removed, and the remaining granulationtissue in the furcation defect is vaporized with the laser. The exposedroot surfaces are then treated with the laser for vaporizing bacteriaand scaled, if calculus is present.

For treatment of degree III furcations, a tunneling procedure isperformed.

Horizontal incisions, directed towards the base of the pocket, are madeat the buccal and lingual sides of the tooth (FIG. 33). Then, thevertical intracrevicular incisions are produced at both sides whichallow the removal of the soft tissue flaps at the furcation entrance andfacilitate the access to the furcation (FIG. 34). Then, the granulationtissue in the furcation is excised by means of a horizontal incision andremoved with a curette or forceps (FIG. 35). The root surfaces aredisinfected with the laser, and the remaining calculus, if present, isremoved with a curette. Then, the patient is instructed in the use ofinterdental brushes in the opened furcation. In case of post-surgicalbleeding, move the fibre over the operated area for a few seconds tocoagulate the blood vessels.

Post-operative Care and Healing

During the laser surgery, a layer of connective tissue is preserved onthe alveolar bone. Therefore, periodontal dressing is not applied aftersurgery. The operated area is rinsed with 0.2% chlorhexidine for a week.Thereafter, tooth brushing is reinstituted and a patient is instructedin the use of cleaning devices for self-performed plaque control.Epithelization of the wound is usually complete after 1-2 weeks with theestablishment of a junctional epithelium adjacent to the root surface(FIG. 7). After laser surgery a healthy dentogingival unit is formedlocated at an apically displaced level in comparison with that atbaseline.

Example 3 TREATMENT OF DENTINAL HYPERSENSITIVITY

The suggested hypotheses behind this finding is closing of the openeddentin tubules with a thin layer of silica during laser therapy. Hightemperature achieved at the tip of an optic fibre, held in contact witha root surface during laser firing, facilitates an even deposition ofsilica on the root surface, thus, resulting in decrease or eliminationof tooth hypersensitivity.

Laser parameters

Treatment of hypersensitive teeth should be performed in two phases. Atthe beginning of the therapy, patients are extremely sensitive to waterand air, therefore, the following parameters are used in the initialphase:

Power: 2-3 W Water: 1-2 Air: 1-2 Time: 15-25 seconds

The laser fibre is always held parallel to the root surface.

This treatment results in the initial deposition of the silica layerover the dentinal tubules and decrease of hypersensitivity.

In the second phase the following parameters are used:

Power: 4-5 W Water: 3-5 Air: 3-5 Time: 10-20 seconds

The laser fibre is always held parallel to the root surface.

Increase in power is correlated with increase water and air irrigationwhich protects the root surface and the pulp from thermal damages duringlaser firing. Such laser therapy provides successful long term decreaseof tooth hypersensitivity in periodontal patients.

Example 4 EVALUATION OF TREATMENT OF PERIODONTAL POCKETS WITH LASER

Introduction

In Periodontics the majority of treatments used for the control ofsupra- and subgingival microflora is provided by scaling and rootplaning. This mechanical therapy has been successfully used not only forthe treatment of periodontal disease, but also for the maintenance ofthe treatment outcome on a long term basis (Badersten et al. 1981,Pihlstrom et al. 1983, Ramfjord et al. 1987). Scaling and root planing,however, is not always efficient in removal of all bacterial depositsand hard concrements from the diseased root surface, which may favourbacterial recolonisation of the periodontal pockets, thus leading to therecurrence of the disease (Rabbani et al. 1981, Stambaugh et al. 1981,Caffesse et al. 1986, Sherman et al. 1990).

In a number of studies the efficacy of mechanical therapy has beencompared to that of systemic administered antibiotics (Listgarten et al.1978, Quee et al. 1987), or local application of antibiotics alone(Ainamo et al. 1992, Pedrazzoli et al. 1992, Goodson et al. 1991) orantimicrobials in conjunction with scaling and root planing (Lindhe etal 1983, Mombelli et al. 1989, Magnusson et al. 1989). Theses studiesindicated that administration of systemic or local antibiotics resultedin successful clinical outcomes. However, the risk of bacterialresistance to antimicrobials may restrict the use of this type oftreatment only for specific situations.

Example 4 EVALUATION OF TREATMENT OF PERIODONTAL POCKETS WITH LASER

Introduction

In Periodontics the majority of treatments used for the control ofsupra- and subgingival microflora is provided by scaling and rootplaning. This mechanical therapy has been successfully used not only fortreatment of periodontal disease, but also for maintenance of thetherapy outcome on the long term (Badersten et al 1981, Lindhe et al.1983, Pihistrom et al. 1983, Ramfjord 1987). Scaling and root planing,however, is not always efficient in removal of hard concrements from thediseased root surface, which may favour bacterial recolonisation, thusleading to tile disease recurrence (Stambaugh et al. 1981, Caffese etal. 1986, Sherman et al. 1990).

In a number of studies the efficacy of mechanical therapy has beencompared to that of systemic antibiotics (Listgarten et al. 1978, Queeet al. 1987), local antibiotics (Aimano et al. 1992, Pedrazzoll et al.1992, Goodsen et al. 1992) or antimicrobials in conjunction with scalingand root planing (Lindhe et al 1983, Mombelli et al., 1989, Magnusson etal. 1989). Also theses studies indicated that administration of systemicor local antibiotics favoured clinical outcomes, the risk of bacterialresistance to antimicrobials restricts their use only for specificpatients or sites. Thus, it required a search for a therapy which isefficient in improvement of periodontal parameters, when used alone orin combination with mechanical treatment.

Recently it has been suggested that short-duration pulsed Nd:YAG lasershave a potential for application in soft tissue-removal procedures dueto minimal bleeding during surgery, which improves visibility to theoperator and decreases surgery time. Pain and postsurgical complicationsare rare (Epstein 1991, Roshkind 1991, White et al. 1991). This type oflaser needs a considerably less amount of generated heat, thus limitingcollateral damages in the tissues adjacent to the treated area. Laserenergy vaporise organical debris, including plaque and calculus, thusproviding their efficient removal (for review see Myers 1991, Midda &Renton-Harper 1991, Midda 1992). Several in vitro and in vivo studieshave shown a significant reduction or eradication of the putativepathogens adherent to root and calculus surfaces following localapplication of Nd:YAG laser (Tseng & Liew 1990, Tseng et al. 1991, Whiteet al. 1991, Cobb et al 1991). Few SEM observations, however, indicatedthat Nd:YAG laser induced root surface alterations, which directlyrelated to the energy level or exposure time (Cobb et al. 1991, Morlocket al. 1992, Trylovich et al. 1992), Thus, contradictory informationexists regarding the application of lasers in the subgingivalenvironment. Recently, new types of Nd:YAG laser has been developedwhich contains water and air irrigation for prevention of overheatingand tissue alteration in tissues, adjacent to the target area. To date,there are no clinical studies evaluating the effect of subgingivalcurettage with this type of Nd:YAG laser.

The purpose of this study was to compare the effect of the subgingivaltreatment with laser versus scaling or combined laser/scaling therapy inadult patients with moderate or sever periodontitis.

Material and Methods

Experimental Design

The study was carried out as a single blind, randomised clinical trial,comparing the efficacy of three subgingival treatments: scaling(S-group), laser (L-group) and laser followed by scaling (L/S-group)versus each other and untreated control (C-group). A split mouth designwas used, i.e. each patient received one of the three treatmentsrandomly assigned to one of the three quadrants of the mouth whereas thelast quadrant served as untreated control.

Patients Criteria

15 patients (8 males and 7 females), ranging in age from 34 to 74 years(mean 49) with evidence of moderate to severe periodontitis wereselected for the study. Each patient presented at least two teeth ineach of 4 quadrants with a pocket, depth 5 mm in at least one of 4 sitesof each tooth, except for third molars. Exclusion criteria includedmechanical and antibiotic therapy within last 3 months, localisedjuvenile periodontitis and compromised systemic condition. Each patientsigned an informed consent.

Clinical Monitoring

At the initial examination (1 months prior to base line) the probingpocket depth (PPD) was recorded at 4 sites of each tooth: mid-buccal,mid-oral, distal and mesial (interproximally, a site with the greatestPPD buccally or lingually was chosen). PPD was measured to the nearestmillimeter, using a coded Hu-Friedy PCP 12, with a 0.4 mm tip diameterand 1 mm graduations from the gingival margin to the tip of the probewhen placed in the pocket The sites with furcation involvement wereexcluded. All subjects, who fulfilled the inclusion criteria wereselected for the study. At this examination they received full mouthsupragingival scaling, polishing and oral hygiene instruction.

At baseline, all sites with PPD 4 mm were treated and used forevaluation of pockets distribution within the groups prior and aftertreatment However, only the sites with PM>4 mm were determined as theexperimental sites for evaluation of changes in pocket depth clinicalattachment level (CAL) and proportions of sites with plaque (PL) andbleeding on probing (BOP). CAL was recorded from the cemento-enameljunction or a top of the tooth crown to the tip of the probe when placedin the pocket. Plaque accumulation (1: presence of plaque, otherwise 0),bleeding on probing (1: if bleeding appeared within 10 seconds afterprobing, other-wise 0) were recorded at the 4 sites of all teeth. Allregistrations were performed at baseline, 1 and 3 months post therapy byone investigator (JJ), who was unaware of the type of treatment assignedfor each quadrant.

Treatment

At baseline, two randomly chosen quadrants received laser treatment,followed by scaling in one of those. The third quadrant was scaled,while the last quadrants was not treated. 1 months after, sites withbleeding on probing received a repeated treatment, assigned to thespecific quadrant. Laser treatment was carried out using the followingparameters average power—4.25 W, water spray-setting 7, airspray-setting 3, frequency—60 Hz, pulse width—250 μsec, duty cycle—30sec per site. Laser treatment was effected by slow insertion of theoptic fibre, aligned parallel to the root surface into a pocket whileactivating the laser. This resulted in gradual and painless placement ofthe fibre to the bottom of the pocket. The optic fibre was then slowlywithdrawn from the pocket while activating the laser. Each site wastreated for 30 seconds. All treatments were performed by oneinvestigator (NL).

Statistical Method

Proportions of the sites with PL per quadrant were calculated out oftotal number of experimental sites in the quadrant. Proportions of thesites with BOP per quadrant were calculated out of total number ofexperimental sites in the quadrant.

The effect of each treatments was evaluated by comparing the mean changein PPD and CAL at 1 and 3 months versus the baseline measurements bymeans of the paired t-test.

Comparisons of efficacy of the 4 treatment regimes were based on averagechance in pocket depths and attachment levels in each quadrant frombaseline to 1 and 3 months and were evaluated by the paired t-tests.

Proportion of the sites with PL, BOP and % of pockets with PPD<4, 4-6and >6 mm were calculated in each quadrant at 0, 1 and 3 months andcompared by the paired t-tests. The significance level is chosen asα=0.05 in all tests.

Results

All treatments were uneventful in all patients during the follow-up.

Table 1 presents the mean values for clinical parameters recorded atbaseline. No statistically significant differences were observed in theproportions of sites with plaque and bleeding on probing, mean PM andpockets distribution within the treatment groups (all p>0.05). At 1month, the proportions of sites exhibiting plaque were decreased versusbaseline in all groups, however, the statistically significantdifference was found only in the C-group (0.42 to 0.24) (FIG. 1). At 3months post therapy, the reduction in number of sites with plaque wasnot statistically significant (p>0.05) in all groups.

The proportions of sites with bleeding on probing were significantlysmaller after laser therapy alone (0.69 to 0.41) or in combination withscaling (0.67 to 0.40) at 1 month versus baseline (FIG. 2). The S-grouppresented less sites with BOP (0.57) than the C-group (0.66), however,significantly more than the L-group or the US-group. Thus, significantlymore sites received repeated seating than other therapies at thisobservation period. At 3 months, the proportions of sites exhibiting BOPwere significantly lower in all groups versus the baseline.

All treatments resulted in significant pocket depth reduction from 0 to1 month in comparison with the non treatment, with the highest change of0,97 mm in the sites subjected to laser/scaling therapy (Table 2).However, the statistically significant reduction in PP13 from 0 to 3months was found only in the sites treated with the combined therapy. Nodifference was found in PPD-reduction between 0-1 and 0-3 months in anygroups.

Statistically significant CAL gain from the baseline to 1 months wasobserved in the scaling (0.55 mm) and laser/scaling group (0.91 mm)versus the control group (0.48 mm) (Table 2). At.3 months, small nonstatistically significant CAL-gain (range 0.34-0.57 mm) was found in allgroups versus the baseline (Table 2).

The % of pockets <4 mm, which did not exist at baseline, wassignificantly greater in all treatment groups versus the control 1 monthpost therapy. However, at 3 months, only the US-group and S-groupcontained significantly more shallow pockets than the C-group. Thereduction of the % of deep >6 mm pockets was significant following thelaser/scaling or laser therapy at 1 month Prom the baseline, andfollowing the combined therapy or scaling at 3 months. Gradual reductionin the % of pockets 4-6 mm was found in all 4 groups at 1 and 3 monthsfrom the baseline.

At the end of the treatment phase, on the question regarding thepreferable treatment all patients have chosen the laser therapy.

Discussion

The results of this randomised single blind controlled clinical trialindicated that laser treatment demonstrated similar to scaling effect onimprovement of all clinical parameters in moderate and deep periodontalpockets. The mean change in PM in the laser treated sites was 0.76 and0.79 mm at 1 and 3 months post therapy what was slightly higher than0.62 and 0.70 mm achieved following scaling. Similarity in terms ofCAL-gain was also observed between the laser treatment (0.68 and 0.54mm) and scaling (0.55 and 0.54 min) at 1 and 3 months follow-up. Thesevalues agree with the data from several studies, evaluating the effectof subgingival scaling (Cercek et al. 1983, Ramfjord et al. 1987,Haffajee et al. 1997) or systemic or local antimicrobials (Listgarten,et al. 1978, Lindhe et al. 1983, Wennström et al. 1987, Eckles et al.1990, Ainamo et al. 1992) on clinical improvement of pocket depth andattachment level. Both treatments resulted in a similar decrease of thepercentage of deep pockets or sites with plaque, and an increase ofpercentage of shallow pockets after 1months, while at 3 months, scalingwas more efficient in improving of those parameters. This, however, maybe explained by a greater number of sites subjected to repeated scalingat 1 months due to bleeding on probing. Thus, laser therapy was moreefficient in reduction of BOP, a risk factor for future attachment lossand disease progression (Lang et al. 1989, 1990), than scaling 1 monthpost treatment. This observation is not surprising due to antimicrobialeffect of Nd:YAG laser, shown in studies in vitro and in vivo (Tseng etal. 1991a, White et al. 1991, Cobb et al. 1992). Obviously, In thepresent study the combined laser/scaling therapy was most beneficial illdecrease of PPD (0.97 and 0.99 mm) and CAL (0.91 and 0.57) 1 and 3months post therapy. These results are supported by the data from an invitro study by Tseng et al. (1991) and SEM study by Cobb et al. (1991)which demonstrated that laser therapy followed by scaling was moreefficient in calculus removal from the periodontally involved rootsurface than laser done. Furthermore, the removal of lased calculusrequired significantly less strokes than non lased ones.

In addition, the changes in the clinical parameters observed postlaser/scaling therapy are in accordance with those reported followingscaling supplemented with local antimicrobials in other studies(Nakagawa et al. 1991, van Steenberghe et al. 1993, Newman et al. 1994).However, the results of the present study disagree with the findingsfrom the investigation by Radvar et al (1990) in which Nd:YAG laserfailed to improve clinical parameters of periodontal disease.

Several in vitro or SEM studies indicated that treatment of the rootsurface with laser may induce surface alteration, related to the time ofexposure and energy levels (Cobb et al. 1992, Morlock et al. 1992,Trylovich et at. 1992). The Nd:YAG laser used in the present studycontained water and air irrigation which in combination with a lowexposure time (30 s per site) reduced the overheating of the subgingivaltissues during laser activation. No complications have been observedpost treatment and most of the patients experienced no or minimal painwhich was lower than following scaling.

A reversal in the CAL-gain observed at 3 months in all treatment groupsmay most likely be explained by the absence of the professional oralhygiene control throughout the study. The predominate number of moderate5 mm pockets, found in this study at baseline, may also have influencedthe values of PPD and CAL-reduction. The pattern of low attachment levelgain at sites with a moderate initial pocket depth has been previouslydescribed (Pihiström et al., 1983, Ramfjord et al, 1987).

In conclusion, the data of this study revealed: 1) Nd:YAG laser showedsimilar to scaling effect in treatment of moderate and deep periodontalpockets; 2) combined laser and scaling therapy resulted in mostbeneficial improvement of all clinical parameters. However, histologicalinvestigations evaluating the effect of this type of laser have yet tobe conducted.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A dental system for laser gingivectomy ofperiodontal pockets, comprising: a handpiece for directing laser lightand a coolant spray towards a target tissue area to be surgicallytreated; said handpiece comprising: a housing with an input end and anoutput end; an optical fiber duct for receiving and holding an opticalfiber and extending within the housing from the input end to the outputend; an optical fiber positioned in the optical fiber duct and having afiber output end for emission of the laser light; a seal positioned inthe optical fiber duct and adapted to receive and hold the optical fiberin water tight engagement with the optical fiber duct; an air duct fortransmission of compressed air and extending within the housing from theinput end to the output end; and a water duct for transmission of waterand extending within the housing from the input end and beinginterconnected with the optical fiber duct within the housing betweenthe output end and the seal so that water flowing in the water ductleaves the housing at the output end through the optical fiber duct; andan apparatus, said apparatus comprising: a laser for emission of laserlight into the optical fiber, the laser being adapted to perform lasergingivectomy in that it has a wavelength ranging from 1.06 μm to 1.07 μmand emits light pulses having a duration ranging from 200 μs to 300 μsat a repetition rate ranging from 55 Hz to 65 Hz and having intensitiesgiving an average power ranging from 1 W to 10 W; a water control memberadapted to be interconnected between a water supply and the water ductand to control the amount of water flowing into the water duct; an aircontrol member adapted to be interconnected between a supply ofcompressed air and the air duct and to control the amount of compressedair flowing into the air duct; and a controller for controlling theoperation of the system and being connected to the water control memberand the air control member and being adapted to set the amount of waterflowing into the water duct in the range from 5 ml/min to 50 ml/min andto set the pressure of compressed air flowing into the air duct so thata coolant spray of mixed air and water is formed whereby efficientcooling of tissue surrounding target tissue being cut by the laser lightis provided.
 2. The system according to claim 1, wherein the controlleris adapted to set the amount of water flowing into the water duct in therange from 10 ml/min to 30 ml/min.
 3. The system according to claim 1,wherein the controller is adapted to set the amount of water flowinginto the water duct to approximately 20 ml/min.
 4. The system accordingto claim 1, wherein the laser is adapted to emit light pulses with arepetition rate of approximately 60 Hz.
 5. The system according to claim1, wherein the laser is adapted to emit light pulses with a pulseduration of approximately 250 μs.
 6. The system according to claim 1,wherein the laser is adapted to emit light pulses with an average powerranging from 3 W to 8 W.
 7. The system according to claim 6, wherein thelaser is adapted to emit light pulses with an average power ranging from4 W to 6 W.
 8. The system according to claim 7, wherein the laser isadapted to emit light pulses with an average power of approximately 5 W.9. The system according to claim 6, wherein the laser is adapted to emitlight pulses with an average power ranging from 5 W to 8 W.
 10. Thesystem according to claim 9, wherein the laser is adapted to emit lightpulses with an average power ranging from 6 W to 7 W.
 11. The systemaccording to claim 1, wherein the laser is adapted to emit light for aperiod ranging from 10 s to 1 minutes upon user activation.
 12. Thesystem according to claim 11, wherein the laser is adapted to emit lightfor a period ranging from 20 s to 50 s upon user activation.
 13. Thesystem according to claim 12, wherein the laser is adapted to emit lightfor a period of approximately 30 s upon user activation.
 14. The systemaccording to claim 1, wherein the controller comprises a timer foraccumulation of the time during which light has been emitted by thesystem.
 15. A dental method for gingivectomy of periodontal pockets,comprising the steps of: emitting laser light from an optical fiber heldin a handpiece, the laser light being adapted to perform lasergingivectomy in that it has a wavelength ranging from 1.06 μm to 1.07 μminto the optical fiber, it is emitted in pulses having a pulse durationranging from 200 μs to 300 μs at a repetition rate ranging from 55 Hz to65 Hz and having intensities giving an average power ranging from 1 W to10 W; emitting a coolant spray of water and air from the handpiece inthe direction of the emitted laser light by transmission of compressedair and water in the handpiece along the optical fiber, the amount ofwater flowing along the optical fiber being in the range from 5 ml/minto 50 ml/min, the pressure of compressed air flowing along the opticalfiber being adjusted so that a coolant spray of mixed air and water isformed; and directing the emitted laser light and the coolant spraytowards a target tissue area to be cut whereby efficient cooling oftissue surrounding target tissue being cut by the laser light isprovided.
 16. A method of laser curettage of periodontal pockets,comprising the steps of: emitting laser light from an optical fiber heldin a handpiece; emitting a coolant spray of water and air from thehandpiece in the direction of the emitted laser light by transmission ofcompressed air and water in the handpiece along the optical fiber, theamount of water flowing along the optical fiber being in the range from5 ml/min to 50 ml/min, the pressure of compressed air flowing along theoptical fiber being adjusted so that a coolant spray of mixed air andwater is formed; and directing the emitted laser light and the coolantspray towards a target tissue area to be treated whereby efficientcooling of tissue surrounding target tissue being treated by the laserlight is provided, wherein the optical fiber is maintained in asubstantially parallel position to the root of the tooth undertreatment, the method further comprising the steps of: positioning ofthe optical fiber in contact with epithelium at the entrance to thepocket to be treated; inserting the fiber into the pocket by moving thefiber in the bucco-lingual direction in proximal sites and in themesio-distal direction in buccal or lingual sites; moving the fiber incontact with the soft tissue apically to the bottom of the pocket andinto contact with the root surface whereby pocket epithelium andgranulation tissue are removed and the root surface is disinfected; andwithdrawing the fiber coronally from the pocket.
 17. A method of lasersurgery on periodontal pockets, comprising the steps of: emitting laserlight from an optical fiber held in a handpiece; emitting a coolantspray of water and air from the handpiece in the direction of theemitted laser light by transmission of compressed air and water in thehandpiece along the optical fiber, the amount of water flowing along theoptical fiber being in the range from 5 ml/min to 50 ml/min, thepressure of compressed air flowing along the optical fiber beingadjusted so that a coolant spray of mixed air and water is formed; anddirecting the emitted laser light and the coolant spray towards a targettissue area to be treated whereby efficient cooling of tissuesurrounding target tissue being treated by the laser light is provided,wherein the optical fiber is maintained in a substantially horizontalposition during treatment, the method further comprising the steps of:identifying depth and type of the pocket to be treated; incising thefiber superficially at the bottom of the pocket to be treated; movingthe fiber through the gingiva; and removing excised tissue with acurette or pincer.
 18. The method according to claim 17, furthercomprising, at interproximal sites, the steps of: moving the fiberthrough the gingiva at buccal and oral aspects; lifting loose tissuewith a pincer or curette; separating loose tissue from the interdentalperiodontium with the fiber; and disinfecting the exposed root surfacewith the laser light.
 19. A method of laser surgery on periodontalpockets, comprising the steps of emitting laser light from an opticalfiber held in a handpiece; emitting a coolant spray of water and airfrom the handpiece in the direction of the emitted laser light bytransmission of compressed air and water in the handpiece along theoptical fiber, the amount of water flowing along the optical fiber beingin the range from 5 ml/min to 50 ml/min, the pressure of compressed airflowing along the optical fiber being adjusted so that a coolant sprayof mixed air and water is formed; and directing the emitted laser lightand the coolant spray towards a target tissue area to be treated wherebyefficient cooling of tissue surrounding target tissue being treated bythe laser light is provided, wherein the optical fiber is maintained ina substantially 45° angle in relation to a longitudinal axis of thetooth to be treated, the method further comprising the steps of:gradually incising the fiber towards the bottom of the pocket whiledissecting; and removing the granulation tissue and pocket epitheliumwith a curette.
 20. A method of laser furcation treatment of periodontalpockets, comprising the steps of emitting laser light from an opticalfiber held in a handpiece; emitting a coolant spray of water and airfrom the handpiece in the direction of the emitted laser light bytransmission of compressed air and water in the handpiece along theoptical fiber, the amount of water flowing along the optical fiber beingin the range from 5 ml/min to 50 ml/min, the pressure of compressed airflowing along the optical fiber being adjusted so that a coolant sprayof mixed air and water is formed; and directing the emitted laser lightand the coolant spray towards a target tissue area to be treated wherebyefficient cooling of tissue surrounding target tissue being treated bythe laser light is provided, the method further comprising the steps of:horizontally incising the fiber to the base of the pocket undertreatment; removing the dissected soft tissue flap; vaporizing theremaining granulation tissue in the furcation defect; and disinfectingthe root surface with laser light.
 21. A method of laser furcationtreatment of periodontal pockets, comprising the steps of emission oflaser light from an optical fiber held in a handpiece, emission of acoolant spray of water and air from the handpiece in the direction ofthe emitted laser light by transmission of compressed air and water inthe handpiece along the optical fiber, the amount of water flowing alongthe optical fiber being in the range from 5 ml/min to 50 ml/min, thepressure of compressed air flowing along the optical fiber beingadjusted so that a coolant spray of mixed air and water is formed, anddirecting the emitted laser light and the coolant spray towards a targettissue area to be treated whereby efficient cooling of tissuesurrounding target tissue being treated by the laser light is provided,the method further comprising the steps of: horizontally incising thefiber to the base of the pocket in the buccal site of the tooth undertreatment; horizontally incising the fiber to the base of the pocket inthe lingual site of the tooth under treatment; removing soft tissueflaps by horizontal intracrevicular incisions at both sites; excisinggranulation tissue in the furcation by horizontal incision of the fiber;and removing granulation tissue with a pincer or curette.